Hrm, this is a hard one to answer without sounding like an asshole. Some religious people I look down on for certain; scientologists, diehard creationists, theists who openly and proudly use their religion for the purpose of bigotry, and the like fall in that category. However, some religious people I look up to, despite completely disagreeing with many of their beliefs: Martin Luther King Jr., Pope John Paul II, Mahatma Ghandi, the Dalai Lama, and other such people who, despite their flaws (sometimes extremely glaring flaws), definitely did something good with their lives far beyond anything I could hope to achieve. That, of course, leaves the vast majority of the religious people who are neither saints nor psychopaths. What about them?
I disagree with them, obviously. Their proof for god is usually limited to "because" or "God is love" or some other groan inducing bit of "proof". But these people can range from profoundly stupid to wildly intelligent in every possible iteration of lifestyles, experience levels, jobs, etc. Do I look down on them all? Certainly not. A lot of people were raised with religion and don't know any better. And, as I'm finding out, a lot of those who people know atheists are ok with them. They aren't necessarily saying I should marry their daughters, but when I ask them if they think I'm going to hell for disagreeing with them, they don't hesitate when they tell me of course not.
The next group of theists are the "you're going to hell for being an atheist" types. This group consists of another dichotomy: the people who feel bad that I'm going to hell and want to help and the people who are looking forward to watching me burn in hell from heaven. The people who genuinely believe I'm going to hell, but just as genuinely want to help me find Jesus to save me, really, I'm ok with. I will rip right into them if they start a religious argument, don't get me wrong, but I appreciate that compassion is what leads them. It's entirely possible that they, as rational human beings, have looked at the same evidence that I did and came to a different conclusion. That happens all the time. I don't think they're right, but that's not a reason to look down on them.
That leaves "holier than thou" theists who don't care about compassion. I have no problems telling you that I look down on these people. However, there's an an entertaining parallel here: these theists who say "I know better than you and therefore I am better than you" have mirrors in the atheist world. I have experience with atheists who say they look down on all religious people. I don't really like the "I'm smarter than you" atheists any more than I like "holier than thou" theists. As far as I'm concerned, they're all assholes.
So do I look down on the religious? Sometimes, but usually no.